This invention relates to in-line flow meters and more specifically to retainer and support devices for in-line flow meters.
Flow meters have a range of applications such as in water meters for houses, meters for medical diagnostic instruments, meters for measuring fuel flow in airplanes and meters commonly known as anemometers. The principles underlying these various meters are often the same, though the structures are different. For example, the principle underlying the anemometer and the aircraft fuel flow meter is a rotor disposed in the fluid flow path turning on a stator mounted on a stationary member. The rotational velocity of the rotor constitutes a measure of the fluid flow parameter sought to be measured. Such is the general principle disclosed in Potter, U.S. Pat. No. 2,270,141.
Potter teaches a rotor comprising a shaft split longitudinally in the middle so that the split portions, when spread apart and twisted slightly, form two spaced apart arcuate vanes, the rotor being supported by a stator. The stator is held stationary at each end about four sides of the stator by retaining means comprising three or four resiliently deformable cylinders. The cylinders are retained at their outer surfaces by the walls of the flow channel.
The vanes of the rotor contain a bar magnet which produces a varying magnetic field when the flow of the fluid past the vanes causes the rotor to spin. Disposed about the outside of the flow channel walls at the point along the length of the channel where the vanes are located is means for sensing the rate of change of the magnetic field within the flow channel. The sensing means is then connected by a conductor to a meter or dial calibrated to indicate the parameter of fluid flow sought to be measured. The Potter flow meter is similar in theory to the flow meter contemplated for use with the present invention.
The retaining means of Potter are easy to manufacture but, because of the number of cylinders used at each stator, the apparatus is difficult to assemble. Furthermore, the type of bearings used to support the rotor may dictate the use of a different retaining means.
Another prior art device is used in conjunction with a modified form of the above-described flow meter. The modified flow meter assembly comprises a flow meter housing to be placed in-line with a longitudinal flow channel such as a pipe or tube, and a magnetic field sensor housing attached to the outer surface of the housing whereby a conductor can be attached to the housing for connecting a remote meter or dial to a magnetic field sensor within the sensor housing. Within the flow meter housing, a rotor is rotatably mounted on longitudinally extending stator means parallel to the fluid flow and within the flow channel. The stator means has oppositely facing ends in the shape of nose cones. The prior art device employs a spoked hub to retain and support the stator means, and thereby the rotor, within the flow meter housing. The retainers are in turn secured within the flow meter housing by annular retainer spring clips, one at each end of the flow meter housing, preventing the retaining and supporting means from being moved in a direction away from the rotor and therefore out of the flow meter housing. This form of the retainer is relatively difficult and costly to fabricate because it must be machined. Because the support must be machined, each support is inherently different from the previous one, to varying degrees. Therefore, flow resistance varies from unit to unit.